The present disclosure relates to a mobile communication terminal device, and more particularly, a mobile communications device including moisture detection for use in limiting corrosion in the device.
Mobile communication terminal devices repeatedly exhibit corrosion phenomena in the interior of the housing of the device on metallic electrically conducting surfaces. 70 to 80% of complaints from customers about their mobile communication terminal devices arise from such corrosion phenomena.
Not only the keypad surfaces, however, are affected by the corrosion phenomena. Concerning the components of the device, short-circuits are frequently caused by the products resulting from such corrosion. In the case of devices having rubber mats and/or films, in particular, corrosion phenomena can be observed beneath the rubber mat or film on metallic electrically conducting surfaces.
If a liquid containing water comes into contact with a module having an operating voltage of greater than 1.2 Volts, then, as a result of electrolysis, the water becomes strongly alkaline up to a pH value of 14. Within a short time the alkaline liquid destroys the module as a result of corrosion. Contamination on the module can further accelerate this process. When more recent tin/silver/copper solder types are used, this process is accelerated still further. Liquids containing acids can also result in the development of corrosion.
Splash-proof devices, for example, are produced in order to counter the corrosion problem. These devices, however, also do not ultimately escape the corrosion problem.
A method of providing so-called “sacrificial” anodes is known whereby these modes are the first items to be destroyed by the corrosion. In this manner, other sensitive parts remain spared from the corrosion for a time. When the sacrificial anodes have been used up, however, protection against corrosion is no longer provided.
A method is also known of providing heating resistors as a measure offering corrosion protection, whereby a dry environment is generated in the mobile communication terminal device as a result of the heat dissipated by these resistors. A disadvantage of this methodology, however, is the high power consumption of the device.
A further method is known of containing the corrosion through the application of protective coatings prior to assembly of the devices. A disadvantage in this case is the fact that only restricted repair options then remain available for modules. A further disadvantage is the fact that the contact points of the keypads can not be protected in this manner because they would otherwise be insulated and incapable of operation as a result.
A method is also known of applying a coating by an immersion process when there is no need to pay special attention to any contact surfaces.
A further method is known of applying a carbon coating to the key contacts and test points to prevent corrosion in the device. With regard to a large number of devices, however, the use of a carbon coating as protection against corrosion is not possible on account of the packaging density of the components.
Finally, a method is known of designing generously dimensioned contact surfaces in order to delay the effects of the corrosion, such as in the form of an open circuit between the contacts, for example. However, the corrosion can not altogether be prevented in this manner, at least not in its entirety. There is likewise little opportunity to prevent a growing short-circuit resulting from corrosion.
In addition, from Patent Abstracts of Japan, Vol. 2000, No. 24, 11 May 2001 (2001-05-11) and JP 2001 197175 A (Matsushita Electric Ind Co Ltd), 19 Jul. 2001 (2001-07-19) a mobile communication terminal device is known that includes elements for detecting moisture in the mobile communication terminal device and a memory feature for recording the circumstances under which the detection of moisture takes place.